Synchronization Mechanism

ABSTRACT

A synchronization mechanism for a correlated movement of a seat and a backrest of an office chair contains a basic support placeable on a chair post, a seat support and a backrest support. To provide a synchronization mechanism for which an adjustment of a spring tension to change the “tilting resistance” of the backrest is not required, a mechanism is proposed whereby the backrest support that is pivotable around a swivel axis is directly linked in a pivotable manner to the basic support, and to the rear end section of the seat support, such that a backward tilt of the backrest induces a lifting of the rear area of the seat support. The seat support is so linked to the basic support as to cause a lifting of the front area of the seat support when the user of the office chair “lifts” him/herself up by leaning against the backrest.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuing application, under 35 U.S.C. § 120, of copending international application PCT/EP2006/003655, filed Apr. 21, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application DE 10 2005 020 237.3, filed Apr. 28, 2005; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a synchronization mechanism for a correlated movement of a seat and a backrest of an office chair containing a basic support placed on a chair post, a seat support and a backrest support.

The term “synchronization mechanism” describes assemblies in the substructure of an office chair seat, such assemblies provide the interlinked kinematics that bring about certain relative movements of the seat and the backrest. The, generally upholstered, seat is mounted on the seat support of the office chair. The backrest support that usefully extends backwards from the actual synchronization mechanism supports the backrest of the office chair on an upright cantilever. The seat support and the backrest support are usually flexibly coupled so that a backward tilt of the backrest—caused e.g. by a chair user leaning against the backrest—induces a lowering of the rear edge of the seat.

In order to change the “tilting resistance” of the backrest, such synchronization mechanisms usually incorporate spring assemblies for pre-stressing the synchronization mechanisms. The pre-stress level depends inter alias on the weight of the chair user.

BRIEF SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a synchronization mechanism which overcomes the above-mentioned disadvantages of the prior art devices of this general type, for which an adjustment of the spring tension to change the “tilting resistance” of the backrest is not required.

With the foregoing and other objects in view there is provided, in accordance with the invention, a synchronization mechanism for a correlated movement of a seat and a backrest of an office chair. The synchronization mechanism contains a basic support placeable on a chair post, a seat support having a rear end section, and a backrest support pivotable around a lateral axis and directly linked in a pivotable manner to the basic support and to the rear end section of the seat support, such that a backward tilt of the backrest support induces a lifting of a rear area of the seat support and the seat support linked to the basic support as to cause a simultaneous lifting of a front area of the seat support during the backward tilt of the backrest support.

It involves a system whereby the backrest support that is pivotable around a lateral axis is directly linked in a pivotable manner to, on the one hand, the basic support and, on the other, the rear end section of the seat support in such a manner that a backward tilt of the backrest induces a lifting of the rear area of the seat support. At the same time, the seat support is so linked to the basic support as to cause a lifting of the front area of the seat support.

A basic idea of the invention is that the user of the office chair “lifts” him/herself up by leaning against the backrest. No spring tension adjustment controls as known from the prior art involving intricate control mechanisms (worm gears, cogwheels, threaded rods etc.), are required. This significantly reduces the manufacturing costs of the synchronization mechanism. At the same time it increases the reliability.

Due to the fact that the seat support is lifted not only in its rear area but that a lift of the front area of the seat support occurs at the same time, a synchronous simultaneous upward and backward movement of the seat in a predefined relation to the backrest takes place. Due to the chosen configuration, the opening angle of the backrest can be quite wide compared with the solutions known from the prior art. Thus, extreme back positions are possible as well.

Of special advantage is a configuration where the basic support is connected to the front end of the seat support via a linear guide. This facilitates a synchronized linear movement of the seat with the backrest. Apart from linear guides with straight-lined guide tracks, different guide tracks are naturally also possible. The configuration of the guide, the position of the guide (e.g. the inclination of the guide in relation to the horizontal) etc., facilitate an individual adaptation of the synchronized movement of the seat support. It is, for instance, possible for the seat support to move synchronously with the backrest in an absolutely linear fashion, without any “tilting” at all. A suitable configuration of the guide also permits a slight “tilting”. Other variations can be achieved by positioning the connection point between the basic support and the seat support at smaller or greater distances from the front edge of the seat.

When the office chair has a seating area configured so that a user imitates any tilting movement of the backrest to a position further back, the so-called “shirt stripping effect” can be prevented very effectively as well.

The lever geometry required for the “self-adjusting” mechanism of the present invention is achieved preferably by a configuration whereby the swivel axis of the connection between the backrest support and the basic support, seen in longitudinal direction of the chair, is positioned behind the hinge axis of the connection between the backrest support and the seat support.

Although, according to the invention, no adjustment of the spring tension is required, a device for adjusting the working area can be provided. This is achieved in an advantageous manner by a spring element disposed preferably in an generally horizontal position in the seat support, such spring element being connected to, on the one hand, the seat support and, on the other, a bearing axle that is positioned crosswise and linked to the basic support. The bearing axle has an eccentric configuration so that by turning it, the user will cause a displacement of the axle center and thus a change in the spring suspension, thereby facilitating an adjustment between at least two spring tension settings (“hard”/“soft”).

Compared with the solutions known from the prior art, the invention introduces a constructively very simple swivel mechanism. This reduces the manufacturing costs. Moreover, despite its simple construction, it significantly reduces the so-called “shirt-stripping effect”. In order words, a very high degree of sitting comfort is achieved without having to resort to complicated and expensive solutions.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a synchronization mechanism, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, rear perspective view of a synchronization mechanism according to the invention;

FIG. 2 is a cross-sectional view of the synchronization mechanism;

FIG. 3 is a top, rear perspective view of the synchronization mechanism; and

FIG. 4 is a cross-sectional, top view of the synchronization mechanism.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a synchronization mechanism that features a basic support 1 to be fitted to a top end of a non-illustrated chair post by a taper socket 2. The synchronization mechanism contains a frame-shaped seat support 3 (see FIG. 3) and in top view a fork-shaped backrest support 4, the cheeks 5, 6 of which are disposed on both sides of the basic support 1. All the drawings show the basic position where the backrest support 4 has a generally vertical position.

A seat 7 with an upholstered surface is mounted on the seat support 3. It is assembled in the customary manner with fastening elements not shown in detail here. The seat 7 is secured firmly to the seat support 3 so that any movement of the seat support 3 will cause a corresponding movement of the seat 7.

Fitted to the backrest support 4 is a backrest, not shown in detail, which in modern office chairs is height-adjustable. The backrest can also be connected with the backrest support 4 as a single unit.

As can be seen from the illustrations, the whole synchronization mechanism, insofar as the actual kinetics are concerned, is configured in mirror symmetry in relation to a central longitudinal plane M (see FIG. 4). The following description therefore always relates to pairs of the structural elements of the swivel mechanism.

The backrest support 4 is attached on the one hand to a swivel bearing 8 on the basic support 1, so that the backrest support 4 is directly hinged to the basic support 1 via a swivel bearing 8. As a result the backrest support 4 with the actual backrest can be tilted in tilting direction S around the swivel axis 9 running through the swivel bearing 8, see FIG. 2. The swivel bearing 8 is formed in front of a front edge 10 of the cheek 5, 6.

On the other hand, the backrest support 4 with the front edge 10 of its cheek 5, 6 is connected via a hinge 11 to a rear end section 12 of the seat support 3. Thus, as a result of a backward tilt of the backrest the seat support 3 is carried along in tilting direction S and also lifted due to the lever arrangement formed by the cheek 5, 6. In other words, there is a swing around an axis 13 of the hinge 11.

As seen in a longitudinal direction 14 of the chair, the swivel axis 9 of the connection of the backrest support 4 to the basic support 1 is fitted behind the hinge axis 13 of the connection of the backrest support 4 to the seat support 3. Moreover, the hinge axis 13 of the connection of the backrest support 4 to the seat support 3 is situated above the position of the swivel axis 9 of the connection of the backrest support 4 to the basic support 1.

The basic support 1 contains two wings 16, 17 running in the direction of a seat support front edge 15. As can be seen in FIG. 3, the wings 16,17 are each guided in a linear sliding guide 18 of the front area of the seat support 3 and connected to one another by a bearing axle 19.

Due to this design, it is not only the rear area of the seat support 3 that experiences a lift H1 when pressure is placed on the backrest and the backrest support 4 tilts back downwards in tilting direction S, see FIG. 2. In addition, the front area of the seat support 3 is lifted in a synchronous manner (lift H2). In other words, there is a simultaneous lift of both the front and the back of the seating area. The seat 7 is lifted in its entirety.

The padding 20 of the seating surface, see especially FIG. 2, is made of formed foam. It is divided into two different seating areas 21, 22, arranged behind one another in longitudinal direction 14 of the seat and differing with regard to their upholstering. With the form of seating surface used in the present example, the front seating area 21, which constitutes about 30% to 40% of the total length of the upholstery 20, is fitted with “standard” upholstery thickness, while the rear seating area (between 70% and 60% of the total length) is fitted with variable upholstery that permits the user to sink in towards the back by way of rolling back. In the example shown, the upholstery thickness of the rear seating area 22 is higher by at least 20 mm compared with the upholstery thickness of the front seating area 21. The manner of transition from the front seating area 21 to the rear seating area 22 is preferably very soft and smooth without any ridges. Particularly good results are achieved with a transition area in the form of an elongated horizontal S.

The transition from the front seating area 21 to the rear seating area 22 is so arranged that the user in a normal (“average”) seating position will put his weight mainly on the front seating area 21. When pressure is put on the backrest, the user's pelvis rolls over the horizontal S into the rear seating area 22. The user thus follows the movement of the backrest back downwards. In other words, the user's backward movement and the connected pressure on the seat 7 in the rear area leads to a “yielding” of the seat and with it a gliding into the upholstery 20 by the user in the form of rolling. A highly synchronized sequence of movements between the backrest and the user is achieved in this way. The so-called “shirt stripping” effect can be significantly reduced as a result.

The foam is preferably free towards the rear seating surface end 23 so that it can expand backwards. To achieve this, an open design of the upholstery 20 without any bordering elements at the back is preferred.

The concept ‘upholstery’ is understood to mean any type of flexible design of the seating surface, regardless of the material used. Apart from formed foams, any other elastic materials may be employed, such as spring packets, or combinations of materials, such as e.g. foam in conjunction with silicon cushions. The use of e.g. dual zone foam is possible as well.

The firmness of the “tilting resistance” of the backrest in the example shown can be switched between two stages from “hard” to “soft”. For this purpose, a tension spring 24 fitted in a generally horizontal position in the seat support 3 is provided, which with its front end 25 is attached to the eccentric bearing axle 19 and with its rear end 26 to the seat support 3. The bearing axle 19 can be turned around its axis from a first to a second position by an operating element 27 fitted at the side (see FIG. 4). Due to the eccentric design of the bearing axle 19, see FIG. 4, the position of the front attachment of the tension spring 24 is changed as well when the bearing axle 19 is turned. The initial stress of the tension spring 24 changes accordingly. Thus, a more or less firm tilting resistance is achieved relative to the position of the bearing axle 19. The number of tension springs 24 is not restricted to one. Depending on the design, further tension springs 24 can be fitted in parallel.

To arrest the inclination of the backrest, there is obviously a mechanism provided, which is not described in detail here but which is operated by a lever 28. 

1. A synchronization mechanism for a correlated movement of a seat and a backrest of an office chair, the synchronization mechanism comprising: a basic support placeable on a chair post; a seat support having a rear end section; and a backrest support pivotable around a lateral axis and directly linked in a pivotable manner to said basic support and to said rear end section of said seat support, such that a backward tilt of said backrest support induces a lifting of a rear area of said seat support and said seat support linked to said basic support as to cause a simultaneous lifting of a front area of said seat support during the backward tilt of said backrest support.
 2. The synchronization mechanism according to claim 1, further comprising a guiding connecting said basic support to said seat support.
 3. The synchronization mechanism according to claim 2, wherein said guiding is a linear guiding.
 4. The synchronization mechanism according to claim 1, wherein, as seen in a longitudinal direction of the office chair, a swivel axis of a connection of said backrest support to said basic support is fitted behind a hinge axis of a connection of said backrest support to said seat support. 